I always wanted to have a line lock on my original 1967 Charger, but I don't like the idea to modify the originality of the car.
I checked on Ebay for a discrete valve...

I found a Whitey B-43F4 Brass Ball Valve - 1/4in - 0.9 CV - 40 Series for $15.00 + 4.95 shipping and installation 2 hours.

Works Great